The invention relates to vacuum fluorescent devices and particularly to those vacuum fluorescent devices having a grid element positioned between a filament and the anodes of the device. The anodes of the device are coated with a fluorescent material so that when excited by bombardment of electrons, the fluorescent material will emit visible light. The brightness of the emitted light from the phosphor is dependent upon the anode current and acceleration potential between the filament and the anode. In these devices, the grid element is disposed between the filament, acting as a hot cathode, and the anode to control the flow of electrons from the cathode to the anode and emission of light from the fluorescent anode. The electric circuit is such that the grid is given a positive potential in order to provide an accelerating potential for electrons passing through the grid to the anode.
Many of the vacuum fluorescent devices are manufactured for use in a high brightness environment. The maximum brightness available from the device limited by the electrical current drive capabilities of commercially available integrated circuits. Thus a tradeoff has been made in the prior art devices between the desired maximum brightness level and the drive currents available to provide the emission of the fluorescent light.